Dynamically loaded suspension for contact recording

ABSTRACT

The present invention mounts a contact recording transducer/suspension assembly over a magnetic recording disk such that the rotation of the disk creates an additional dynamic loading to counteract the lift-off forces generated by rotation of the disk. As the rotation rate of the disk is increased and lift-off forces grow, so do the offsetting dynamic loads created by the transducer/suspension assembly. Optionally, the cross section of the transducer/suspension assembly is modified to further improve this dynamic loading effect. 
     The present invention mounts the transducer/suspension assembly in a contact recoding disk file so as to place the assembly in compression once disk rotation is initiated. The assembly is mounted so that the frictional force between the assembly and the disk &#34;pushes&#34; the assembly against its mounting instead of applying a &#34;pulling&#34; force on the assembly.

This is a continuation of application Ser. No. 08/023,528, filed Feb.26, 1993, now abandoned.

TECHNICAL FIELD

The present invention relates generally to rotating magnetic storagedevices and their recording elements and more particularly to the sliderassembly of a contact recording storage device.

BACKGROUND OF THE INVENTION

Conventional magnetic disk drives are information storage devices whichutilize at least one rotatable magnetic media disk with concentric datatracks, a read/write transducer for reading the data from or writing thedata to the various tracks, an air bearing slider for holding thetransducer adjacent to the track generally in a flying mode above themedia, a suspension for resiliently holding the slider and thetransducer over the data tracks, and a positioning actuator connected tothe transducer/suspension combination for moving the transducer acrossthe media to the desired data track and maintaining the transducer overthe data track during a read or a write operation.

The suspension is required to maintain the transducer and the slideradjacent to the data surface of the disk with a low controlled loadingforce. The actuator positions the transducer over the correct trackaccording to the data desired on a read operation or to the correcttrack for placement of the data during a write operation. The actuatorpositions the transducer over the correct track by shifting thetransducer/suspension combination generally transverse to the track.

The air bearing slider supports the transducer above the disk with acushion of air that is generated by the rotating disk. Because therecording density of a magnetic disk drive is limited by the height ofthis air cushion between the transducer and the media, a goal of airbearing slider design is to "fly" the slider as close as possible to themagnetic media while avoiding physical impact with the media.

Alternatively, the transducer may operate in contact with the disk.Touching the media presents unique problems in wear and, duringoperation of the disk file, the possibility of a catastrophic impactbetween the transducer and an asperity on the media. To minimize theseproblems, it has been recognized that the loading force on thesuspension system must be reduced to a low level. A variety ofmechanisms have been disclosed which attempt to implement such a contactrecording disk file. Structured to work in a perpendicular recordingenvironment, these devices permit the head and suspension to be easilymanufactured. U.S. Pat. Nos. 5,041,932; 5,073,242; and 5,111,351entitled "Integrated Magnetic Read/Write Head/Flexure/ConductorStructure" granted to Harold J. Hamilton disclose an integral magnetictransducer/suspension structure having the form of an elongateddielectric flexure or suspension body with a magnetic read/writetransducer embedded at one end. Integral transducer/suspensionassemblies of this general form are sometimes referred to as "reed"devices because of their rough similarity in shape to a reed for amusical instrument. In a preferred embodiment, Hamilton discloses anelongated, dielectric flexure body of aluminum oxide having a magneticpole structure and helical coil integrally formed at one end of theflexure body with embedded copper conductor leads running the length ofthe flexure body to provide electrical connection for the transducer.The integral structure is fabricated utilizing conventional vapordeposition and photolithography techniques.

As noted above, contact recording permits higher recording densitiesunaffected by variations in flying height. The rate at which suchrecorded data can be read from or written to the magnetic recordingdevice is inherently limited by the rate at which the magnetic mediaspins. Higher rotation rates are desirable since they result in fasteraccess to data. Unfortunately, high spin rates in combination with thelow static load of a contact recording transducer/suspension assemblycan cause the transducer to lose contact with the magnetic media. Thisphenomena is known as "lift-off" of the transducer from the media. Thelinear speed at which the lift-off occurs is known as the lift-offvelocity. For a given disk rotation rate, the lift-off problem is moresevere at the outer radius of the disk where the highest relative linearvelocity between the media and the transducer is experienced.

This lift-off problem is typically addressed by increasing the staticload on the suspension assembly and thereby increasing the force thatmaintains the transducer in contact with the media. This solution hasthe undesirable effect of increasing the wear caused by the slidingcontact of the transducer and the disk surface. High wear rates limitthe useful life of the magnetic disk drive and, if high enough, mayrender the device impractical. Furthermore, increased suspension loadingincreases the likelihood that contact with a disk asperity will damagethe transducer/suspension assembly. In addition, increased static loadon the suspension increases the stiction force between the transducerand the media at zero velocity. Overcoming this force during the startof disk rotation can damage the disk and the transducer/suspensionassembly. For the foregoing reasons, there is a need for an apparatusthat addresses the lift-off problem created at high rotation rateswithout increasing the suspension loading force.

SUMMARY OF THE INVENTION

The present invention is directed to an apparatus that satisfies thisneed by mounting the transducer/suspension assembly such that therotation of the disk creates an additional dynamic loading to counteractthe lift-off forces generated by rotation of the disk. As the rotationrate of the disk is increased and lift-off forces grow, so do theoffsetting dynamic loads created by the transducer/suspension assembly.Optionally, the cross section of the transducer/suspension assembly maybe modified to further improve this dynamic loading effect.

More particularly, the present invention mounts thetransducer/suspension assembly so as to place the assembly incompression once disk rotation is initiated. In other words, thefrictional force between the assembly and the disk "pushes" the assemblyagainst its mounting as opposed to prior art devices wherein thefrictional force applied a "pulling" force on the assembly. In addition,the assembly is mounted such that above the media contact point theupper surface of the transducer/suspension assembly forms a small anglewith respect to the disk surface. As this angle is increased the dynamicloading increases for a given rotation rate.

A disk drive having features of the present invention comprises ahousing with at least one rigid data storage disk mounted in thehousing. An actuator arm is positioned in the housing in proximity tothe disk. Coupled to the actuator is a suspension assembly shaped tohave a pad portion. The pad portion is positioned in contact with thedata storage disk. A transducer, located near the pad, reads and writesdata on the storage disk. Means are provided for rotating the disk suchthat a point on the rotating disk moves in the general direction fromthe pad toward the point where the suspension is coupled to theactuator. This places the suspension in compression and greatlyincreases the rate at which the disk can be rotated without causing thetransducer/suspension assembly to lift-off.

This invention thus provides a contact recording transducer/suspensionassembly which maintains contact with a storage disk even at highrotation rates without the deleterious effects of increasing thesuspension's static load. Further features and advantages of theinvention will become apparent from the following specification and theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a disk drive system according to thepresent invention;

FIG. 2 is a top view of a magnetic recording mechanism with a rotaryactuator and employing a reed transducer/suspension assembly inaccordance with the present invention;

FIG. 3 is a cross-sectional view of one embodiment of a reedtransducer/suspension assembly useful in practicing the presentinvention;

FIG. 4A is a cross-sectional view of a reed transducer/suspensionassembly in an unloaded position above a media disk;

FIG. 4B is a cross-sectional view of a reed transducer/suspensionassembly in contact with a media disk;

FIG. 5 is a cross-sectional view of one embodiment of a reedtransducer/suspension assembly in contact with a media disk and mountedin accordance with the present invention; and

FIG. 6 is a cross-sectional view taken along section line A-B of FIG. 2of an alternate embodiment of the reed transducer/suspension assembly ofthe present invention.

DETAILED DESCRIPTION

With reference to FIG. 1, a schematic diagram of a magnetic recordingdisk drive is illustrated and is designated by the general referencenumber 10. System 10 comprises a disk spindle assembly 12 and a headactuator assembly 14. Spindle assembly 12 and head actuator assembly 14are located within a sealed housing 16 to prevent particulatecontamination. Spindle assembly 12 comprises a plurality of magneticrecording disks 20 which are mounted to a spindle 22. Spindle 22 isrotated by an in-hub electrical motor which is not illustrated. Headactuator assembly 14 comprises a voice coil motor 30 which moves anactuator arm assembly 32 relative to the disks 20. Assembly 32 has aplurality of actuator arms 34, each of which is positioned in a spacebetween two adjacent disks 20. Each actuator arm 34 has a pair ofread/write heads 36. One head reads the disk positioned above theactuator arm 34 and the other reads the disk positioned below theactuator arm 34.

In operation, spindle 22 is rotated by the in-hub motor and motor 30moves the actuator arms 34 between the disks 20 to the desired tracklocation. One of the read/write transducers 36 then reads or writes dataon the desired track.

Referring now to FIG. 2, a data recording disk file useful forpracticing the present invention is illustrated. The disk file includesa housing 40 in which is mounted a rotary actuator 42, an associateddisk 44 and a drive means 46 for rotating the disk 44. The rotaryactuator 42 moves a reed assembly 48 in an arcuate path over the disk44. The rotary actuator 42 includes a voice coil motor, which comprisesa coil 50 movable within the magnetic field of a fixed permanent magnetassembly 52. An actuator arm 54 is attached to the movable coil 50. Theother end of the actuator arm 54 is attached to the combinationtransducer-suspension assembly 48.

Referring now to FIG. 3, one embodiment of a suspension/transducer reedassembly useful for practicing the present invention is illustrated. Thecombination suspension/transducer-slider structure 130 comprises anelongated generally rectangular body of a dielectric material such asaluminum oxide (Al₂ O₃) or silicon dioxide (SiO₂), for example, having arelatively uniform thickness along most of its length forming asuspension section 137 and a somewhat greater thickness at one end, theleft end as illustrated, wherein a magnetic read/write transducer orhead 140 is formed along with a slider on a lower side thereof. The termslider refers to the side of the assembly which is generally parallel toand adjacent the media surface in both Winchester-type disk files andcontact recording applications.

As mentioned above, the reed structure 130 will lift-off from the disksurface if the rotational velocity of the disk is high enough. In thiscase a hydrodynamic air bearing will form between the disk surface andthe slider. As shown in FIG. 3, the slider comprises a shaped protrusion133 formed on the lower side of the reed assembly body 131. The surfaceof the shaped protrusion 133 is coated with a wear layer 135 of suitablematerial, such as diamond-like carbon, to minimize wear and damage whenthe reed assembly contacts the media surface. Although protrusion 133 asshown in the figures comprises a simple structure, other embodiments ofthe reed structure can include a multiple-stepped protrusion whichallows the wear layer 135 to continue to provide wear protection to theslider surface even after the magnetic yoke poletips have been exposed,either by wear or by a post-fabrication lapping process intended toreduce the magnetic separation between the head and the disk surfacecaused by the thickness of the wear-resistance layer in the pole tipregion.

The read/write head 140 is formed integrally with the suspension section137 to provide the combination reed assembly 130. The read/write head140 comprises a ring-type head utilized in horizontal recordingapplications, but can alternatively comprise a probe-type head forperpendicular recording applications.

In one embodiment, the combination reed assembly 130 comprises a body131 of Al₂ O₃ having a length of 9 to 12 millimeters (mm), a width of0.5 mm and a thickness of 35 microns for that portion of the body 131forming suspension section 137 and a thickness of 42 to 50 microns forthe read/write head section 133. The reed assembly 130 is fabricatedutilizing well-known deposition and photolithography techniques on abase substrate and is described in greater detail in IBM applicationSer. No. 08/471,108 entitled "Integral Transducer-Suspension Assembliesfor Longitudinal Recording" filed on Jan. 8th, 1993 and herebyincorporated by reference.

A detailed description of another contact recording mechanism useful forpracticing the present invention can be found in U.S. Pat. No. 5,486,963entitled "Integrated Transducer-Suspension Structure for LongitudinalRecording" filed on Aug. 19th, 1992 and hereby incorporated byreference.

Referring now to FIG. 4A, the reed structure 130 of FIG. 3 isillustrated in its unloaded conventional mounting position abovemagnetic recording disk 200. The distance between the surface of thedisk 200 and the bottom of the actuator 160 is exaggerated in the figureand is designated by reference D1. This distance is approximately 1millimeter or greater. The direction of rotation of the disk media isindicated and designated by vector V1. The reed structure 130 istypically coupled to actuator assembly 160 by adhesive bonding toinclined surface 162. Inclined surface 162 forms an angle A1 withrespect to the top surface of actuator 160. This angle is exaggerated inthe figure and is approximately 5 degrees.

In operation of the disk file, actuator 160 would be lowered toward disk200 to bring pad 133 into contact with disk 200. The compliance of reedstructure 130, being approximately 0.5 Newtons/meter, is such that reed130 can bend and allow pad 133 to become parallel to the surface of disk200.

Turning now to FIG. 4B, the reed structure 130 of FIG. 3 is illustratedin its conventional mounting position in contact with a magneticrecording disk 200. The distance between the surface of the disk 200 andthe bottom of the actuator 160 is exaggerated in the figure and isdesignated by reference D2. This distance is approximately 0.5millimeters. The degree of curvature of reed 130 is also exaggerated.The direction of rotation of the disk media is indicated and designatedby vector V2. The reed structure 130 is positioned so that pad 133 is incontact with the disk 200 and an area 135 above the pad 133 is generallyparallel to the surface of disk 200. The static loading on reed 135,given the difference between D1 and D2 and the compliance of reed 130,is approximately 20 milligrams.

In operation the disk 200 rotates in the indicated direction and the pad133 with an imbedded read/write transducer remains in contact with thedisk 200. As discussed above, the structure of FIG. 4B has the problemof the reed structure 130 lifting off from the surface of the disk athigh disk rotation rates. Air near the surface of the disk is moved byfrictional forces in the same direction as the disk rotation. The airflow generated creates a lifting force on reed 130 and eventually thislift overcomes the static loading on the transducer/suspension assembly.If the rotation rate of disk 200 is increased to the point where thelinear velocity of the disk reaches approximately 4 m/s at the point ofcontact, the lift-off forces overcome the static loading force and pad133 separates from disk 200. At this point pad 133 becomes an airbearing surface.

Referring now to FIG. 5, the reed structure 130 of FIG. 3 is illustratedas mounted in accordance with one embodiment of the present invention incontact with a magnetic recording disk 200. The distance between thesurface of the disk 200 and the bottom of the actuator 160 isexaggerated in the figure and is designated by reference letter D3. Thisdistance is greater than D2 and is approximately 0.6 millimeters. Thedirection of rotation of the disk media is indicated and designated byvector V3. The reed structure 130 is coupled to actuator assembly 160,typically by adhesive bonding, and positioned so that pad 133 is incontact with the disk 200 and an area 135 above the pad 133 forms anangle A3 with respect to the surface of the disk.

In operation the disk 200 rotates in the indicated direction and the pad133 with an imbedded read/write transducer remains in contact with thedisk 200. In contrast to the prior art apparatus, the dynamic loading ona reed assembly mounted in accordance with the present inventionincreases as the rotational rate increases. This is caused by air flowdirected against the top surface of the reed structure 130 incombination with a pressure differential created in the area below thereed 130. Therefore, the dynamic load urging the reed 130 towards thedisk increases as the rotational speed of the disk increases. Thiscounteracts the tendency of pad area 133 to become an air bearingsurface at high rotation rates. The magnitude of the dynamic loading isstrongly dependent upon the angle A3 formed between the disk surface andthe top surface of the reed 130 at a point above the contact point. Thelarger this angle, the larger the dynamic force urging the reed 130toward the disk. For example, when A3 is 0.5 degrees, the lift-offvelocity of reed 130 is approximately 8 meters/second. When A3 has avalue of one degree, the lift-off velocity exceeds 10 meters/second.This angle is controlled by varying the difference between the unloadedheight of the actuator, D1 and the loaded height, D3. However, thebottom surface of pad area 133 must be substantially parallel to thedisk 200 surface even though reed 130 is tilted at an angle with respectto the disk surface. There are several alternatives for achieving thisresult. One alternative is to lap the pad area so as to duplicate theangle A3 on the bottom surface. Alternatively, the angle could be formedby photolithographic techniques during the fabrication of the reed 130.

Referring now to FIG. 6, the cross-section of an alternative embodimentof the reed structure 48 of FIG. 3 is illustrated. The cross-sectiondisplayed is taken along section line A-B of FIG. 2. In this embodiment,the cross section of reed structure 130 is modified so as to form ataper. In the case where the reed 48 is composed of a dielectricmaterial such as aluminum oxide (Al₂ O₃) or silicon dioxide (SiO₂), thetaper could be produced by lapping, grinding, or etching techniques asare known in the art. The reed 48 of FIG. 6 is oriented so that bottomsurface 310 is adjacent to the disk surface during operation of the diskfile. The purpose of the shaped cross-section is to maintain a constantdynamic load as the actuator moves from the outside diameter of the diskto the inside diameter. When the actuator arm 54 is accessing an insidedata track, the relative velocity of the disk surface is lower at thecontact point. This results in less of a dynamic load on a reed assemblymounted in accordance with the present invention. Therefore, the taperis added to reed 48 so as to create an additional dynamic load caused byair flowing over surface 300. Optionally, the cross section could bevaried along the length of the reed 48 to optimize the dynamic loadingat various diameters.

Although the present invention has been described in considerable detailwith reference to certain preferred versions thereof, other versions arepossible. For example, the present invention could have benefits whenused with any integrated transducer/suspension assembly designed for lowstatic load contact recording. Similarly, although the invention hasbeen described in the context of rotary actuators, it would be apparentto one skilled in the art that the present invention would have benefitsin a disk file that utilized linear actuators and positioned reedassemblies perpendicular to the actuator's line of travel. It should beapparent that other modifications and adaptations of the describedembodiments may occur to one skilled in the art without departing fromthe scope of the present invention as set forth in the following claims.

We claim:
 1. A contact recording disk drive assembly comprising:ahousing; at least one rigid data storage disk rotatably mounted in saidhousing; an actuator arm positioned in said housing in proximity to saiddata storage disk; a suspension assembly shaped to have a pad portionand having a distal and a proximal end, said distal end of saidsuspension forming a small, non-zero angle of less than five degreeswith respect to the surface of said data storage disk, said pad portionlocated on said distal end of said suspension assembly and positionedfor contact with said data storage disk, said proximal end of saidsuspension assembly coupled to said actuator arm; a transducer locatedat said distal end of said suspension assembly, for reading and writingdata on said data storage disk; and means for rotating said data storagedisk in said housing to move a point on said disk in a directionsubstantially from said distal end of said suspension assembly to saidproximal end of said suspension assembly, such that when air generatedby the rotation of said data storage disk impinges on said small angleof said distal end of said suspension assembly, said pad portion is incontact with said data storage disk.
 2. A contact recording disk driveassembly according to claim 1, wherein said actuator arm is a rotaryactuator arm.
 3. A contact recording disk drive assembly according toclaim 1 wherein said small angle is more than 0.5 and less than fivedegrees.
 4. A contact recording disk drive assembly according to claim1, wherein said small angle is more than 0.5 and less than two degrees.